Manufacture of hydrogen peroxide



United States Patent 4 Claims. ((31. 23-207 This invention relates to an improved process for the manufacture of hydrogen peroxide.

In Canadian Patent No. 673,355 issued on Oct. 29, 1963, there is disclosed a process for the manufacture of hydrogen peroxide by the reduction of the disodium salt of anthraquinone disulphonic acid with hydrogen sulphide and subsequent oxidation of the reduced product with oxygen. The resulting hydrogen peroxide is separated from the alkaline disodium anthraquinone disulphonate solution by precipitation as calcium peroxide by the addition of calcium hydroxide at room temperature. In the carrying out of this process, it has been found that it is ditficult to completely separate the anthraquinone disulphonic acid salt from the precipitated calcium peroxide. The calcium peroxide product is fine grained and usually contains several percent of anthraquinone disulphonic acid salt. This cannot be removed even by the use of unecomonically large amounts of wash water. Since the process recycles the anthraquinone disulphonic acid salt solution, economic operation requires that an efficient separation of the latter be employed. In addition the adsorbed anthraquinone disulphonic acid salt contaminates the hydrogen peroxide product.

It has now been found that effective separation of the anthraquinone disulphonic acid salt solution from the calcium peroxide precipitate can be attained if the calcium peroxide is percipitated in the form of coarse crystals of calcium peroxide octahydrate.

It is therefore an object of this invention to provide an improved process of the above type for the manufacture of hydrogen peroxide wherein the solid calcium peroxide intermediate is readily separated from the solution in which it is formed. Another object is to provide such an improved process for the manufacture of hydrogen peroxide wherein the anthraquinone disulphonic acid salt ingredient employed therein can be recovered and recycled for continuous use. Additional objects will appear hereinafter.

The improved process of this invention comprises reacting an hydrogen sulphide-containing gas with an aqueous solution of a salt of an anthraquinone disulphonic acid, thus producing elemental sulphur and the reduced anthraquinone disulphonic acid salt, separating the sulfur and oxidizing said reduced salt to form hydrogen peroxide thereby regenerating the starting anthraquinone disulphonic acid salt, reacting the hydrogen peroxide thus formed with a soluble calcium compound under conditions that produce a precipitate of coarse crystals of calcium peroxide octahydrate, separating said calcium peroxide crystals from the anthraquinone disulphonic acid salt solution, washing with water any residual anthraquinone disulphonic acid salt solution from the calcium peroxide crystals and recovering hydrogen peroxide from said calcium peroxide.

Alternatively the soluble calcium compound may be mixed with the reduced anthraquinone disulphonic acid salt prior to the oxidation step. In this manner the hydrogen peroxide is precipitated during the oxidation step and before it can react with residual hydrogen sulphide still present in the solution. In this procedure it is not necessary to sweep residual hydrogen sulphide from the solution prior to the oxidation step.

The improvement of this invention lies in the novel method of recovering a calcium peroxide with a low content of anthraquinone disulphonic acid salt from the reaction medium. If the calcium peroxide is precipitated Without special precautlons at room temperature by the addition of calcium hydroxide to a solution containing hydrogen peroxide and anthraquinone disulphonic acid salt the precipitate is usually finely divided. This finely divided precipitate of calcium peroxide, when separated from the solution, retains substantial amounts of the anthraquinone disulphonic acid salt. Effective separation of calcium peroxide from the mother liquor can be a tained if the calcium peroxide is precipitated as coarse grained calcium peroxide octahydrate. There are various conditions of precipitation which can lead to suitable precipitates.

A desirable aid to the obtaining of anthraquinone disulphonic acid sodium salt-free crystals of calcium peroxide octahydrate is a stable hydrogen peroxide containing solution. The cationic impurities can conveniently be removed by ion exchange resins.

It has also been found that calcium peroxide octahydrate changes to the dihydrate form at temperatures above 40 C. However, the temperature of transition is lowered by the presence of hydrogen peroxide in. the surrounding aqueous solution. At 20 C. the octahydrate form is not stable for long periods in concentrations of hydrogen peroxide greater than 0.25% and at 25 C. the maximum concentration of hydrogen peroxide for long term stability of the octahydrate is 0.009%. However, the octahydrate form of calcium peroxide appears to be capable of existence in a metastable form for short periods of time at higher concentrations of hydrogen peroxide than indicated hereinbefore.

The presence of seed crystals of calcium peroxide octahydrate in the hydrogen peroxide containing anthraquinone disulphonic acid sodium salt solution aids in the forming of suitable precipitates. These seed crystals may be added to the solutions or may be present through a continuous process of precipitation.

It has been found that the preferred procedure for precipitating calcium peroxide is to run the aqueous solution of reduced anthraquinone disulphonic acid salt slowly into a well stirred precipitator containing a continuously aerated solution or slurry of calcium hydroxide in excess of the amount required to precipitate the calcium peroxide. The ingredients are maintained below 30 C. The calcium hydroxide concentration is maintained by the continuous addition of calcium hydroxide. In this procedure the hydrogen peroxide concentration in the precipitator will remain at a value less than the stoichiometric equivalent of the calcium hydroxide present. The calcium peroxide octahydrate precipitate prepared in this manner is readily washed free of anthraquinone disulphonic acid sodium salt. In addition the residual hydrogen sulphide in the solution will not reduce the yield of calcium peroxide octahydrate.

It has been found that the use of a solution of calcium hydroxide gives calcium peroxide octahydrate precipitates containing less adsorbed anthraquinone disulphonic acid sodium salt than the use of calcium hydroxide slurn'es.

It has been observed that when an aqueous solution of calcium hydroxide is added to an aqueous 0.6% solution of hydrogen peroxide containing dissolved anthraquinone sulphonic acid sodium salt it is possible to obtain a precipitate at room temperature of calcium peroxide octahydrate in spite of the high concentration of hydrogen peroxide. It is believed that the octahydrate crystals so formed are metastable.

When solid calcium hydroxide is added directly to an aqueous solution of hydrogen peroxide containing anthraquinone disulphonic acid sodium salt the precipitate formed is fine grained and the adsorbed anthraquinone diployed. The anthraquinone disulphonate solution may be purified before use by passage through a cation ionic exchange resin.

The calcium peroxide produced by this process may be sulphonate cannot be washed free from the crystals with 5 employed as such or may be used for the production of Water. hydrogen peroxide or of oxygen by known methods.

The precipitated calcium octahydrate can be conven- When the calcium peroxide is converted to hydrogen iently separated from the anthraquinone disulphonic acid peroxide it is essential to remove trace impurities before salt-containing mother liquor by centrifuging and washthe hydrogen peroxide is concentrated by distillation. ing the residual mother liquor from the solid with water. Metallic impurities may be removed by passage of the The solid calcium peroxide can then be dried by known aqueous hydrogen peroxide solution through a cationprocedures. exchange resin such as the sodium salt of the well known Alternatively, the calcium peroxide octahydrate after sulphonated styrene-divinylbenzene copolymers. Traces separation from the mother liquor may be converted to of anthraquinone disulphonate remaining in the aqueous solid anhydrous calcium peroxide by immersion in a hydrogen peroxide solution can be removed by passage dilute aqueous solution of hydrogen peroxide at about through a bed of activated carbon prior to distillation. Re- 30 C. Washing of the anhydrous calcium peroxide prodmoval of the traces of anthraquinone disulphonates in this net with acetone at room temperature provides a matemanner may ermit sim lification of the distillation rocp p p rial containin onl trace amounts of the anthraquinone ess in that the solution need onl be concentrated b Y y y disulphonic acid salt. vaporation of water without the necessity of distilling The h drogen sul hide as suitable for the process off the hydrogen eroxide.

y p g p of this invention ma be ure h drogen sulphide or it may The process of this invention 18 more full illustrated y P y i y be a gas containing hydrogen sulphide and gases inert by the following examples but it is to be understood that with respect to the reactions of the invention such as its scope is not limited to the specific embodiments therenitrogen or gaseous hydrocarbons. Low concentrations in described. of carbon dioxide can be tolerated. However, the presence Examples 1 t0 1 2 n 'n gi gg i 3 g gs gizg l gi ii i g gas W111 series of solutions was prepared containing 0.5% by The anthr uinone disul honates suitable as reactants Welght of hydrogen peroxlde and varylng amounts of an q thraquinone 2,7disulphonic acid disodium salt (ADA) in the process of this invention are the water soluble salts issolved in water. The hydrogen peroxide was precipn of anthraquinone disulphonic acid which do not form tated as calcium eroxide Octah drate b the addit. f precipitates with hydrogen peroxide and include the sodip y y O uni salts of the known isomers of anthraquinone disula solubie calcmm.compound' In some cases seed Crystals phonic acid and mixtures thereof. The disodium salt of of Ca 1clum peroxlde Octahydrate ,Were present Sodmm anthraquinone 2,7-disulphonic acid is the most water soluchloride w added to the sohmon to f as a f ble of the isomeric sodium salts and, being commercially to determme f amoumflf free 1n the P P available, is the preferred reagent. However, the less tates- The Calcium PeTOXlde Was preclpltated at a soluble salts of the other isomers of anthraquinone di- P 0f -r Separated y centrifuging and the sulphonic acid can be used at lower concentrations but precipitate Washed with water. The results of the separathe concentration of hydrogen peroxide produced will be 40 tions are shown in Table I. The percentages are by less than when the 2,7-disulphonic acid derivative is em- Weight.

TABLE I Concentra- Seed Volume Total in- ADA P tion of crystals, pH during Weight of wash organic produr zt iiiiin Ex. Calcium ADA in percent precipi of wet Solid Water, solids in percent peroxide source solution, of tation cake, milliprecipior total in form of percent product grams litres ate, inorganic CaO2.8H O

percent solids Unwashed cake 0 34. 2 23. 7 1 Solidreagent 12.2 0 260 {Washed cake 534 16.1 30,0

Ca(OH)1. .-..do 1,500 8.8 Unwashed cake- 0 32. 9 17. 6 Washed cake 1, 632 33. 4 5. 6 2 do 8. 1 0 260 After reslurrying 2, 755 34. 2 4. 4 78, 0

with H2O. Partially dehydrated 3, 375 49. 3 4. 35 Unwashed cake 0 37. 1 13. 3 Washed cake 1, 869 37. 7 6. 4 3 do 0. 5 0 260 After reslurrying 3, 097 36. 8 7, 4 33, 0

with H20. 4 Cal Irgartiallly gehidrated 3,498 59.1 7.2

. cium nwas e ca'e 30.1 4.26

chloride. M 0 11 12 273 {Washed cake 1,112 30.5 2. 73 i 5 d0 5.1 33 1041 no {Unwashedcake 0 18.4 0.99 Washed cakc 650 23. 8 0.03 6 do 8.9 163 Unwashed cake 0 32.0 2,1 99 0 7 8 rd Washed cake" 468 31.0 0.39 O1 reagent 4.6 50 n5 Unwashed cak 0 26.9 5.5 100 Ca(OH) Washed cake- 417 27. 3 1. 4 8 Dgsgglllredre- 1.7 0 3 Washed cake 30 30.0 2.23

Ca(OH) nwas e ea c. .1 2.89 15 162 iv i ashed c i ke n 45 28.8 0. 52

nwas e ea c. 31.4 1.63

w 5 ea c. 2.76

((tgllnfllfilfll no 30 {Washed cake 351 30.5 0.08 100 1 Unless otherwise stated the precipitates were centrifuged. 2 Filter.

The efi'ectiveness of employing seed crystals of CaO -8H O in reducing the anthraquinone disulphonic acid salt re The details of the washing of the filtered precipitate of Example 31 with water using a centrifuge is given in the following Table IV.

tained on the washed precipitate is clearly shown. 5

Examples 13 to 18 TABLE IV A series of aqueous solutions was prepared containing Percent ADA Wash wate W h t purified anthraquinone 2,7-d1sulphomc acid disodium salt Percent ADA in washed use r mifiilitr e s gsr (ADA) d hydrogen peroxide The anthraquinone in filter cake precipitateas millilitres 100 gm. of washed percent of Caoz precipitate 2,7-d-1sulphon1c acid salt was purified by passage through a column of the sodium salt of a strongly acidic cation 0 45 1 38 0 0 ion exchange resin constituted by a sulphonated 0:004 0:105 100 70 sty-rene-divinyl-benzene copolymer. The hydrogen per- 8-82 gig; Z88 g oxide was precipitated as calcium peroxide octahydrate 0. 02s 0086 400 280 by the addition of hydrogen peroxide solutions to cal- M31 1095 500 'cium hydroxide slurries or solutions in excess of the stoichiometric amount required to react with the hydrogen peroxide. The ingredients were stirred vigorously E am I 35 during the precipitation. The precipitated calcium perx p e oxide was separated from the mother liquor and washed grams calcium peroxide octahydrate which by analwith water. The results of the separations are shown in ysis contained 32.3% by weight of calcium peroxide were Table II where percentages are given on a weight basis. mixed with 100 millilitres of aqueous hydrogen peroxide TABLE II Hydrogen Percent Hydrate Yield of ADA Couperoxide Weight of CaOz in ADA in 119.0 in active Hydrogen Example Calcium source centration, concen- Washed washed washed washed oxygen in peroxide Tempera- Percent tration, precipitate, precipitate, precipitate precipitate, washed in filtrate, ture,C. Percent grams Percent based on Percent precipitate, Percent CaO; Percent 13 Solid Ca(OH)z 20 0. 438 0. 77 25.0 0.16 48.9 82.0 0.025 25 14. do 20 0.425 9.77 25.4 0.14 56.1 84.0 0.0004 25 15. do 10 0. 498 12. 9s 24. 0 0. 13 56. 3 94. 0 0. 0067 25 16. --do 5 0. 597 11. 53 29. 0 0. 1e 54. 7 92. o 0. 0015 25 17. ,do 18.6 0.455 177.1 21.9 0.15 53.5 95.3 0.0029 224 18 Dissolved Ca(OH)2 18.6 0.468 69.4 28.5 0.030 01.2 58.4 0.0075 22 5 Examples 19 to 34 A series of aqueous solutions was prepared containing anthraquinone 2,7-disulphonic acid disodium salt (ADA) and hydrogen peroxide. The hydrogen peroxide was precipitated by addition to an aqueous slurry or solution of calcium hydroxide, the calcium hydroxide concentration being in excess of the stoichiometric amount required to react with the hydrogen peroxide. In some cases the solutions contained seed crystals of calcium peroxide octahydra-te. The precipitated calcium peroxide was filtered f-rom the mother liquor and washed solution containing 0.25% hydrogen peroxide by weight. The mixture was allowed to stand for 16 hours at 30 C. The product was separated from the liquid by filtration and on analysis was found to contain 52.8% by weight of calcium peroxide. Washing of the product with about 50 millilitres of acetone at room temperature gave a product containing 90.5% by weight of anhydrous calcium peroxide.

When the calcium peroxide octahydrate starting material and the anhydrous calcium peroxide final product were analyzed for anthraquinone disulphonic acid salt it with water. The results of the preparations are shown was found that durmg the conversion process the Value in Table III where the percentages are given on a weight had been reduced from 0.1 1% to 0.045 by weight of basis. the anhydrous product.

TABLE III C2102 in ADA in Yield of ADA Concen- Weight of Seed washed washed active Hydrogen Example Concen- Calcium source tration washed crystals, precipiprecipioxygen peroxide Temperatmtion, M11202, precipipercent tat tate, perin prein filtrate, ture, 0. percent percent tate, grams percent cent of cipitate, percent CaOz percent 20 Solid Ca(OHi) 0. 438 9. 8 25. 6 0. 62 82. 0 0.025 25 20 do 0. 425 9. 8 25. 4 0. 84. 0 0. 0064 25 10 O. 498 13. 0 24. 0 0. 54 94. 0 0. 0067 25 5 0. 597 11. 5 29. 6 0. 54 92. 0 0. 0015 25 18, 6 0. 455 177. l 21. 9 0. 68 95. 3 0. 0029 22-23 18 6 0. 468 69. 4 28. 5 0. ll 58. 4 0. 0075 22-25 20 0. 33 79. 3 44 23. 9 0. 037 90 6 0. 0024 25 15 0. 40 59. 5 30 19. 3 0. 64 52. 7 0. 0074 23 10. 8 0. 27 70. 2 50 23. 0 0. 065 80. 2 0. 0030 24 10. 8 0. 63 79. 6 50 29. 1 0. 12 93. 5 0. 0025 23 11, 0 0.5 154 31. 0 0. 02 1- 3 11, 0 0. 5 154 32. 9 0. 088 1- 3 10. 8 0. 143 28 32. 7 0. 095 77. 0 0. 0015 23 15 0. 40 77. 7 52 23. 8 0. 126 84. 2 23 1,5 0. 090 3. 6 22. 3 0. 112 79. 4 0. 003 24 10 2. 0 30. 0 28. 5 1. 2 0. 289 23 7 Example 36 To 4 liters of an aqueous solution containing 0.267 mole per litre of anthraquinone 2,7-disulphonic acid sodium salt was added at room temperature by means of a tritted glass disperser sufficient hydrogen sulphide gas to provide 0.1191 mole per litre of H 8. No residual hydrogen Sulphide was detected in the solution. The sulphur product was filtered off and weighed and found to be 0.1056 mole per litre of the solution.

The reduced anthraquinone disulphonate solution was added slowly at room temperature to a stirred slurry of calcium hydroxide in aqueous anthraquinone disulphonate solution through which air was being blown. The calcium hydroxide was in excess of that required to react with the hydrogen peroxide formed by the oxidation of the reduced anthraquinone disulphonate solution. The reduced anthraquinone disulphonate solution was added sulficiently slowly that it was oxidized almost immediately. When the oxidation was complete the calcium peroxide precipitate was filtered, washed with water and analyzed. The calcium peroxide product calculated as CaO was equivalent to 0.0953 mole per litre. This was a yield of 80.0% based on the hydrogen sulphide used and a yield of 88.6% on the basis of the sulphur recovered.

What we claim is:

1. In a process for the manufacture of hydrogen peroxide wherein an hydrogen sulphide-containing gas is reacted with an aqueous solution of an alkali salt of an anthraquinone disulphonic acid, thus producing elemental sulphur and the reduced anthraquinone disulphonic acid salt, the sulphur being separated and the reduced anthraquinone disulphonic acid salt oxidized to produce hydrogen peroxide, the improvement whereby the hydrogen peroxide thus formed is separated as coarse grained readily filterable calcium peroxide octahydrate which comprises adding the aqueous alkaline solution of the reduced anthraquinone disulphonic acid salt to a stirred aqueous solution of a water soluble calcium compound which is continuously aerated with an oxygen-containing gas, the solution being maintained at a temperature below 30 C., the rate of addition of the reduced anthraquinone disulphonic acid salt being such that the concentration of the calcium compound remains in stoichiometric excess of that required to precipitate the hydrogen peroxide formed by the oxidation of the reduced anthraquinone disulphonic acid salt, thus precipitating coarse grained calcium peroxide octahydrate, separating said calcium peroxide from said solution, washing residual solution from said calcium peroxide with water and recovering hydrogen peroxide from said calcium peroxide.

2. A process as claimed in claim 1 wherein the water soluble calcium compound is calcium hydroxide.

3. A process as claimed in claim 1 wherein, prior to conversion to hydrogen peroxide, the calcium peroxide octahydrate is converted to anhydrous calcium peroxide by treating said calcium peroxide octahydrate with aqueous hydrogen peroxide solution at about 30 C., separating the solid product from the hydrogen peroxide solution and washing said product with a water-miscible organic solvent.

4. A process as claimed in claim 3 wherein the watermiscible organic solvent is acetone.

FOREIGN PATENTS 10/1963 Canada.

OSCAR R. VERTIZ, Primary Examiner.

H. S. MILLER, Assistant Examiner. 

1. IN A PROCESS FOR THE MANUFACTURE OF HYDROGEN PEROXIDE WHEREIN AN HYDROGEN SULPHIDE-CONTAINING GAS IS REACTED WITH AN AQUEOUS SOLUTION OF AN ALKALI SALT OF AN ANTHRAQUINONE DISULPHONIC ACID, THUS PRODUCING ELEMENTAL SULPHUR AND THE REDUCED ANTHRAQUINONE DISULPHONIC ACID SALT, THE SULPHUR BEING SEPARATED AND THE REDUCED ANTHRAQUINONE DISULPHONIC ACID SALT OXIDIZED TO PRODUCE HYDROGEN PEROXIDE, THE IMPROVEMENT WHEREBY THE HYDROGEN PEROXIDE THUS FORMED IS SEPARATED AS COARSE GRAINED READILY FILTERABLE CALCIUM PEROXIDE COCTAHYDRATE WHICH COMPRISES ADDING THE AQUEOUS ALKALINE SOLUTION OF THE REDUCED ANTHRAQUINONE DISULPHONIC ACID SALT TO A STIRRED AQUEOUS SOLUTION OF A WATER SOLUBLE CALCIUM COMPOUND WHICH IS CONTINUOUSLY AERATED WITH AN OCYGEN-CONTAINING GAS, THE SOLUTION BEING MAINTAINED AT A TEMPERATURE BELOW 30*C., THE RATE OF ADDTION OF THE REDUCED ANTHRAQUINONE DISULPHONIC ADID SALT BEING SUCH THAT THE CONCENTRATION OF THE CALCIUM COMPOUND REMAINS IN STOICHIOMETRIC EXCESS OF THAT REQUIRED TO PRECIPITATE THE HYDROGEN PEROXIDE FORMED BY THE OXIDATION OF THE REDUCES ANTHRAQUINONE DISULPHONIC ACID SALT, THUS PRECIPITATING COARSE GRAINED CALCIUM PEROXIDE OCTAHYDRATE, SEPARATING SAID CALCIUM PEROXIDE FROM SAID SOLUTION, WASHING RESIDUAL SOLUTION FROM SAID CALCIUM PEROXIDE WITH WATER AND RECOVERING HYDROGEN PEROXIDE FROM SAID CALCIUM PEROXIDE. 